Apparatus for operating gaseous discharge devices



Jung 25, 1957 w. oGLEsBr-:E Erm. 2,797,366

APPARATUS FOR OPERATING GASEOUS DISCHARGE DEVICES Filed Jan. 22. 1952 3 Sheets-Sheet 1 asf WHEN

AWITNESSES: INVENTORS Wendell Oglesbee 8 Wm e Archie R. Cornell.

ha a @www A BY mim ATTORNEY June 25, 1957 w. oGLEsB'EE ETAL 2,797,366

l APPARATUS FR OPERATING GASEOUS DISCHARGE DEVICES Filed Jan. 22. 1952' 5 Shee'tS-Sheet 2 WITNESSES: INVENTORS Wendell Oglesbee 8 BY Archie R. Cornell. 'U' W @klm June 25, 1957 w. oGLEsBl-:E ETAL APPARATUS PoR OPERATING GAsEous DISCHARGE DEvIcEs 3 Sheets-Sheet 3 Filed Jan. 22. 1952 Fig.

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INVENTORS VWendell Oglesbee 8 BY Archie Cornell. @AJM ATTORNEY United States Patent C) APPARATUS FOR OPERATING GASEOUS DISCHARGE DEVICES Wendell Gglesbee, Lakewood, and Archie R. Cornell, Avon Lake, Ghio, assignors to Westingheuse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application January 22, 1952, Serial No. 267,627 1 Claim. (Cl. 315-138) This invention relates generally to apparatus for starting and operating gaseous discharge devices, such as iluorescent lamps, and to the manner in which such apparatus and discharge devices are related, and more specifically to transformer and ballast provisions for a pair of such discharge devices.

When a plurality of electric gaseous discharge devices, of which the uorescent lamp is one example, are operated together, it has been the practice to energize them from a single low voltage source through a transformer to obtain a higher voltage than the source voltage for operating the lamp. Generally, the transformer is of the auto-transformer type with the discharge devices connected in parallel with the transformer secondary, there being a separate ballast in the form of an inductance with a magnetic core connected in series with each lamp to stabilize its operation, and to provide an additional voltage necessary to starting the discharge devices. Also, in order to provide a high power factor and to correct for stroboscopic effect the circuit of one discharge device is made a leading circuit by the inclusion of a series capacitor. The several transformer and ballast coils have required a relatively large amount of copper and iron, and although attempts have been made to reduce their size and weight, as by mounting them on a common core, little progress has been made in this direction.

It is, therefore, one object of this invention to provide a novel unitary combined transformer and ballast assembly for the control of a. plurality of gaseous discharge devices of the cold or hot cathode types, which is on the order of one-third less in weight and size than such assemblies heretofore employed, and has a comparable reduction in electrical losses.

Another object of this invention is to provide a novel transformer and ballast assembly for the control of a plurality of gaseous discharge devices connected therewith in lead and lag circuit relation, wherein the ballast for one of said devices is a high reactance secondary winding of the transformer, and the ballast for another of said devices is independent of the transformer at least during operation of said devices after they have been started.

Another object of this invention is to provide a novel transformer and ballast assembly for the control of a plurality of gaseous discharge devices, wherein all of the devices are supplied from a single transformer and yet the devices operate independently of each other, in that failure of one device will not appreciably change the current of the remaining ones.

Another object of this invention is to provide a novel transformer and ballast assembly for the control of a plurality of gaseous discharge devices, wherein the size of the ballast for one of said devices is materially reduced by reducing the volt-amperes to which the coil thereof is subjected.

Still another object of this invention is to provide a novel transformer and ballast assembly for the control of a plurality of gaseous discharge devices, wherein the core structure for the transformer and the ballast coils has individual openings for receiving the coils of such respective devices so that each opening may be designed for its respective coil or coils.

A Istill further object of this invention is to provide a novel assembly of transformer and ballast coils on a single core for controlling operation of a plurality of gaseous discharge devices.

Another object of this invention is to provide a novel unitary coil and core assembly for the coils of a transformer and ballasts for use in controlling operation of a plurality of gaseous discharge devices.

These and other objects of this invention willbecome more apparent upon consideration of the following detailed description of preferred embodiments thereof, when taken in connection with the attached drawings, in which:

Figure 1 is a top plan view of a transformer and ballast assembly for the control devices constructed in accordance Fig. 2 is an end view Fig. 3 is a side elevation view of the assembly shown in Figs. l and 2,

Fig. 4 is a top plan view of a modified form of transformer and ballast assembly,

Fig. 5 is a side elevation view of the assembly shown in Fig. 4,

Fig. 6 is a schematic view of the transformer and ballast assembly shownin Figs. 1 to 3, together with the circuit for connecting it to the discharge devices,

Fig. 7 illustrates the connections of the coils employed in the assembly shown in Figs. 1 to 3 and 6,

Fig. 8 illustrates the connections of the coils employed in the assembly shown in Figs. 4 and 5, and

Fig. 9 is a schematic View similar to Fig. 6, except that it shows certain of the coils in different locations.

In accordance with this invention, the transformer and ballast coils for controlling the operation of a plurality of gaseous discharge devices, such as liuorescent lamps, are all assembled on a common core structure. While this invention is hereinafter specifically described in connection with the operation of a pair of lamps, it is not limited to this specific number of lamps, but may be embodied in the control for operation of a greater number of lamps. The coils for operation of a pair of lamps are assembled in a manner such that the ballast coil for the lag lamp is in the same mangetic circuit with the transformer, whereas the ballast coil for the lead lamp is outside the magnetic circuit for the transformer coil but employs as part of its magnetic circuit a portion of the magnetic circuit for the transformer. As the detailed description proceeds, the benefits flowing from this design with respect to reduction in size and weight of the assembly will become apparent.

The transformer `and ballast assembly 2 shown in Figs. 1, 2 and 3 is supported on an elongated core structure 4, which is built up from a plurality of laminat-ions 5, and includes a central longitudinally extending winding leg portion 6 and a pair of yoke portions 8 positioned at opposite sides of the windin-g leg portion 6. Although the core structure 4 is herein disclosed as composed of laminations, each of which is in three parts forming the winding leg portion and yoke portions, respectively, this specific arrangement per se forms no part of this invention but is more specifically described and claimed in our copending application Serial No. 267,628 on Core, filed concurrently with this application and assigned to the same assignee `as this application. For the broad purpose of this invention, each lamination 5 could be 'constructed in yone integral piece, though preferably it is of more than one piece, such as the three pieces herein illustrated.

The core structure with this invention,

of gaseous electric dischargeV of the assembly shown in Fig. 1,

4 -has three pairs of opposed openi t ings 12, 14 and 16 provided in the yoke portions 8 thereof at opposite sides of the winding leg portion 6, and spaced along the length of the core structure, with the opposed openings 12 adapted to receive a lag coil 18 wound on windingleg portion 6. The opposed openings 14 are for the purpose of receiving the transformer winding'2ll wound on the windingleg portion 6, and the opposed openings 16 are for the purpose of receiving va lead coil 22 also wound on winding leg portion 6 at the location f openings 16. Intermediate lag'coil 8 and transformer winding 20, the yoke portions of the core structure are provided with opposed legs 24which extend inwardly between the two windings 18 and 2t) toward winding leg portion 6, but terminate short thereof to form a leakage gap in the core structure between the openings 12 and 14. The yoke portions 8'of the core structure also have opposed inwardly extending leg portions 26 which extend into engagement with the winding legportion 6 at theleft end `of the core structure, as viewed in Fig. l of the drawings, and it has opposed inwardly extending leg portions 28 likewise extending intov engagement with winding leg portion 6, but the legs 28 are located between the transformer winding 20 and the lead coil 22. At the righthand end of the core structure, as viewed in Fig. 1, the yokeA portions 8 thereof have lopposed inwardly extending legs 30 which preferably terminate short of eachother. There is also another gap 32 formed between the righthand end of winding leg portion 6A and the legs 30 of yoke portions 8.

For the purpose of making connection to the coils 18, 20 and 22, ra terminal plate 34, preferably of an electrical insulating material, such as ber or the like, is secured to one face of the assembly 2 in engagement with the respective windings, by any suitable means, such, for example, as by cementing or by the cords 35. The terminal plate 34 carries a number of terminals for the respective coils comprising the terminal 36 for lag coil 18, terminal 38 which acts as a second terminal for lag coil 18 and for a tap on transformer winding 20, terminal 40 is `connected to another tap on the transformer winding 20and terminals 42, 44 and 46 are connected with taps on the lead coil 22.

When the-core structure 4 is formed `of three-piece laminations, as illustrated in Fig. l, and as is more particularly pointed out in the labove-mentioned copcnding application, the laminations may be secured together in any desired manner, preferably as by welding them at the three exterior junctures of the three parts of each lamination, namely, at the junctures 48 and Si) between the legs`26' of the yoke portions 8 and the adjacent end of winding leg portion 6, and at the gap 52 between the legs 30 of yoke portions 8. lf desired, additional securing means, such as the bolt 54, which extends through aligned apertures in winding leg portions 6, may also be employed.

The assembly shown in Figs. 4 `and 5 has most of the parts constructed in a manner similar to the parts of the assembly shown in Figs. l, 2 `and 3, and accordingly such parts are indicated by the same reference numerals with the addition of a prime thereto. Thus, the yassembly 2 includes an elongated core structure 4 composed of laminations 5 which are shaped similar to the laminations 5 shown in Figs. l, 2 and 3. For example, the core structure 4 includes a winding legrportion 6 andyoke portions 8' forming at opposite sides opposed opening 12', 14' and 16' spaced along the length of the `core structure in each of the yoke portions 8. As in the previously described embodiment of this invention, the openings 12' in the core` structure receive a lag coil 18', the openings 14 receive the transformer winding 20 and the `openings 16 receive the lead coil 22', with all of these coils being mounted on the winding leg 6 of the core structure. The yoke portions 8 of this core structure are also provided with opposed inwardly extending legs 24' intermediate the transformer winding 14 and lag coil 12 which terminate short of the winding leg 6' to provide a gap therebetween. The yoke portions 8' also have their end legs 26 in engagement with the adjacent end of winding leg portion 6', and have opposed inwardly extending legs 28 located between the transformer winding 20 and the lead coil 22' extending into engagement with the winding leg portion 6. At the opposite end of the core structure 4 the yoke portions 8' thereof have inwardly extending opposed legs 30 which. preferably terminate short of each other. There is 'also a gap 32 between the winding leg portion 6 and the legs 30' of the yoke portions 8'.

Instead of a terminal plate, the terminals in this embodiment of the invention are mounted directly on the coils themselves and include a terminal 36 for the lag coil 18', terminals 38' and 40 for the transformer winding 20', and Va terminal 42 for the lead coil 22.

As in the previously described embodiment of the invention, the three pieces of the laminated core may be secured together by welding at the three points /l-S, 59 and 52', and in addition to a securing bolt 54 extending through the winding leg portion 6', an additional bolt 56 may be provided for tightening clamp bars 58 against opposite sides of the assembly.

The manner in which the various coils of the transformer and ballast assembly are electrically connected, as well as the manner in which they are associated with gaseous discharge devices,`\vill be better understood by reference to Figs. 6 and 7 of the drawings, wherein a pair of fluorescent lamps 60 and 62 are illustrated as being controlledby the assembly shown in Figs. l to 3 of the drawings. Each lamp is adapted to be mounted in a pair of lamp holders located at opposite ends thereof, such as the lamp holders 64 provided for receiving the lamp 60, and making electrical contact to the terminal pins 61 of the lamp, and holders 66 for holding the lamp 62 at opposite ends and making electrical contact to the terminal pins 63 of this lamp. While the lamps 60 and 62 are shown as being of the instant start or cold cathode type, it will beunderstood that the invention is equally applicable to the preheat type of lamp in which case the arrangement would differ from that illustrated in Fig. 6, only in that each lamp holder would have a pair of contacts for engaging two terminal pins at each end of each lamp, with a circuit connecting the two extra lamp terminals controlled by a suitable starting device.

Fluorescent'lamps are generally installed where they are to be operated from a low voltage supply source, such as or 220 volts commonly supplied consumers of electricity, and such a source of supply may be connected to supply conductors 68 and 70, with the conductor 68 being controlled by a-switch 72 inserted in `series circuit relation therewith. In accordance with this invention. the supply conductors 68 and 70 are connected to the primary part 74 of transformer winding 20. It will be apparent from the drawing that the transformer is herein illustrated in the form of an auto-transformer having a primary coil portion 74 and a secondary coil portion 76. Supply conductors 68 and 70 are connected to the primary coil portion 74 of the transformer winding 20. The secondary portion 76 of the transformer winding is connected to the lead ballast coil 22 and it, in turn, is connected by a conductor 78 having a condenser 80 in series therewith to one holder 64 for lamp 60, the other holder thereof is connected to the supply conductor 76. Lamp 62 also has one end thereof connected to supply conductor 70, and the other end is connected by conductor 82 to the lag coil 18 and the circuit then proceeds to the same tap on the transformer winding 20 to which supply conductor 68 is` connected.

It will benoticed that the core 4 provides a low reluctance magnetic circuit for the transformer winding 20 comprising the parts of winding leg portions 6 and yoke portions 8 between the legs 26 and 28, as well as these legs themselves. The auto-transformer thus acts in the well-known manner to generate voltage in the secondary part 76 of its winding, which winding, together with the primary part 74, is connected across the lamp 60, so that the voltage in the secondary part 76 of the transformer winding is added to that of the primary portion to thus provide the necessary high voltage for operation of the lamp 60. While the lead coil 22 is included in the supply circuit for lamp 60, the gaps between legs 30 and the adjacent end of winding leg portion 6 of the core determines the reactance for this coil at the value desired. The gap between legs 30 themselves, while not essential, is desirable to insure proper assembly of the parts of each lamination, particularly to insure proper engagement of yoke legs 26 and 28 with winding leg 6, and thus properly determine the gaps between yoke legs 24 and winding leg 6.

Lamp 62 is connected across the primary portion 74 of the transformer winding and lag coil 18. Since lag coil 18 is in the same magnetic circuit as the transformer winding, a voltage is induced in it which adds to the source voltage to provide the necessary high voltage needed for operation of the lamp 62. However, lag coil 18 acts somewhat diiferently than the secondary portion 76 of the transformer winding, in that the legs 24 of the yoke portions of the core provide for magnetic leakage between the transformer winding 20 and the lag coil 18, and the gap between these legs and the winding leg portion 6 provides for a high reactance of the lag circuit containing lag coil 18. vIt will be apparent that lag coil 18 may be designed to produce in conjunction with the primary portion 74 of the transformer winding a starting voltage for the lamp 62 which will be substantially the same as that provided by the auto-transformer for lamp 60. Actually the voltage available for starting lead lamp 60 will be somewhat in excess of that provided by the autotransformer above, due to some magnetic coupling between it and the lead coil 22. The lag coil 18 also provides an impedance in series with lamp 62 of a value comparable to that provided for lamp 60 by lead coil 22 and capacitor 80.

Inasmuch as lag coil 18 provides a relatively high reactance in the circuit for lamp 62, it will be apparent that the current in this lamp will lag behind that of the source of supply, whereas the condenser 80 in the circuit for lamp 60 will cause the current in this circuit to lead that of the source of supply to thus provide a relatively high power factor, and correct for stroboscopic effect of the lamps.

Instead yof extending lag coil 18 from the same tap of transformer winding 20 that supply conductor 68 is connected to, it may be tapped into any part of the transformer winding. For example, in Fig. 8 the lag coil 18 is shown as being tapped to substantially the midpoint of the secondary part of the transformer winding, thus dividing the latter into two secondary portions 84 and 86. This change does not materially affect operation of the lamp 60 but may be employed merely to increase the voltage to lamp 62 with the use of a somewhat smaller lag coil 18, inasmuch 'as the portion 84 of the transformer secondary winding is included in the circuit t-o lamp 62. Depending on the value of the supply voltage and the operating characteristics of the lamp, the lag coil 18 may be tapped to any other part of the primary or secondary portion of the transformer winding.

Another feature of this invention resides in the size of the common portions of the magnetic circuit for the transformer winding 20 and that of the lead coil 22. These common portions, comprising legs 28 of the yoke portions 8, may be restricted in cross section area, as illustrated on Figs. l and 6 of the drawings, so that they partially saturate during the open circuit condition of the lead lamp 60. It will be apparent then that by properly phasing the lead coil 22 with respect to the transformer winding 20, namely, by winding these coils so that this induced llux is additive, the open circuit voltage applied to lamp 60 will be substantially higher than the output poses the lead voltage of the auto-transformer due to some of the flux generated by the transformer winding 20 linking with the lead coil 22. By employing this expedient, the size of the auto-transformer winding 20 and core may be reduced for any given open circuit Voltage requirement of lamp 60, while the required voltage for lamp 62 may still be achieved by appropriately designing'lag coil 18. Once lamp 60 starts, the flux in reduced area legs 28 decreases, it then being the vector difference between the auto-transformer flux and that of lead coil 22. When lamp 60 starts, the coupling between the transformer coil 20 and lead coil 22 will be thus reduced so that for all practical purcoil 22 'operates as if it were an entirely separate unit from the auto-transformer. The voltage across the lead coil 22, condenser and lamp 60 all connected in series after the lamp starts is then lower than the open circuit voltage across the auto-transformer and lead coil, in series, and by the same token is lower than the voltage obtained where the lead coil is entirely separate and independent of the transformer. Still another result obviously is that during operation of lamp 60 a reduction in voltage is obtained across condenser 80.

The modification shown in Fig. 9 has transformer winding -20 interchanged with lag winding 18 with respect to their locations along the length of the core structure.

ln Fig. 9, the core 88 includes a'winding leg 90 and identical yoke legs 92 each of which has laterally projecting legs 94 and 96 of the same length for engaging opposite sides of the winding leg 90 and an intermediate shorter laterally projecting leg 98 forming a gap with the winding leg 91). ln addition, a long each yoke leg 92 extends across the adjacent end of the winding leg 90. This is similar to the core 2 previously described except for the positions of the transformer and lag coils previously referred to, and in this case the legs 94 of the yoke legs 92 need not be of restricted cross section as 15 shown.

This change does not materially alect operation of the lamps controlled thereby, since lag coil 18 still remains in the same low reluctance magnetic path through the core structure aslthe transformer winding 19, it still has a leakage path formed by legs 98 between it and the transformer windings, and lead coil 22 remains outside of, but employs a part of, such low reluctance magnetic path.

All of the transformer and ballast assemblies described above have been found to be more economical of construction than has heretofore been practical and have resulted in very substantial savings in the amount of copper and iron employed, thus reducing losses, as well as the size and weight of the assembly. There are a number of factors contributing to this economy in construction, thus, for example, locating the entire transformer winding in one core opening permits the autotransformer coil to be wound in two or more sections so that the size of wire for the inner section of the coil may be reduced for the same amount of copper losses. ln the case of the embodiment of invention shown in Figs. 6 and 7, the secondary portion 76 of the transformer winding may he wound over the primary portion 74, as illustrated in Fig. 6; and in the case of the arrangement shown in Fig. 8, the transformer coil may be wound in three sections with the primary portion 74 again being innermost, the part 84 of the secondary portion being at an intermediate location, and the part 86 being outermost. Another saving is made because the lag coil 18 may be of smaller size than has heretofore been employed where the lead and lag ballast coils are separate and independent of the auto-transformer, because it is required to handle only about one-half the number of volt amperes, and consequently may be about one-half the size of a comparable lag coil which is independent of the auto-transformer. Moreover, it will be apparent that on an abnormal operation, such as when the lead lamp is not operating and the circuit to the lead lamp 60 is open, there will be no overheating inasmuch as all leg 100 at one end ofy aver/,Beet

(Figs..6 and 7)V or a substantial part.(Fig. 8) of the auto-transformer secondary will then be out of the circuit, and, therefore, not contributing any heat to the assembly. can be. designed for a greaterI flux density and consequently may have fewer turns than arrangements where the auto-transformer is independent of the lead and lag4 ballast coils but supplies high voltage to both. A very substantial saving in the amount of magnetic material for core structure 4 .is achieved because all of the` coils comprising the auto-transformer and lead and lag ballast coils are mounted on and employin their magnetic circuits cornmon core parts. Thus it has previously been pointed out that lag coil 13 is in the same low reluctance magnetic circuit as the .transformer winding 20, and even though lead coil 22 is not, it employs in part of its magnetic circuit, a` portion (legs 28) of the magnetic circuit of transformer winding 20.

Having described preferred embodiments of the invention in accordance with the patent statutes, it is desired that the invention be not limited to, these specific constructions, inasmuch as `it will be apparent that many modifications in addition to those specifically pointed out herein may be made without departing from the broad spirit and scope of this invention. Thus as mentioned at the outset, additionalrlamps may be controlled, for eX- ample, an additional lag lamp could be controlled merely` by extending the core `to include an additional lag coil in the same magnetic circuit and making the transformer of the proper size. Accordingly, it is desired that this invention be interpreted as broadly as possible and that it be limited only as required by the prior art.

We claim as our invention:

Apparatus for controlling operation of a plurality of This means that the aut-transformer coil.

gaseous discharge .devices comprising, `a transformer havlag reactor coil in the same magnetic circuit with said transformer windings, a magnetic leakage path in said l core structure between said transformer windings and said lag reactor c'oil, and said corestructure having a third portion supporting said lead reactor coil out of the low reluctance magnetic circuit of said transformer windings, but having a part located in part of the magnetic circuits of said lead reactor coil and transformer windings, said last mentioned part of the core structure being substantially smaller in section than any other portion of said magnetic core structure so as to provide some magnetic coupling duringopen `circuit conditions of said lead reactor coil between the transformer windings and said lead reactor coil.

References Cited in the tile of this patent 30 UNITED STATES PATENTS 

